1. Field of the Invention
The present invention relates to a semiconductor device with a connected wiring layer structure electrically connecting upper and lower conductive layers to each other and a method of fabricating the same.
2. Description of the Related Art
With recent reduction in design rules, an insulating film serving as a spacer is sometimes provided on an outer periphery of a connected wiring layer in order to prevent electrical contact, short or electrical interaction between wiring layers adjacent to each other. More specifically, for example, JP-A-H06-310612 discloses a peripheral structure of a connected wiring layer connecting one wiring layer to another wiring layer. In the disclosed technique, an insulating film is provided around a wiring layer (corresponding to a connecting-wiring layer). The insulating film prevents contact between wiring layers or a wiring layer and a semiconductor substrate. The insulating film further suppresses reduction in the reliability due to corrosion. Since the insulating film is formed by chemical vapor deposition (CVD), it can be applied to the sides and the back as well as the upper side of the wiring layer, thereby composing an effective insulating structure.
JP-A-2002-198421 discloses the structure of a connected wiring layer connecting one wiring layer to another wiring layer. In the disclosed technique, an insulating film is selectively retreated relative to buried interconnection connecting conductor layers so that surfaces of the conductor layers are exposed, whereby a contact area is increased.
However, when an insulating film is formed as a spacer on the outer periphery of the wiring layer at a step and an upper conductive layer is formed at a subsequent step, the upper conductive layer can be brought into contact only with an upper surface of the connected wiring layer.
The design rules have recently been scaled down further and accordingly, a contact area cannot be increased when the upper conductive layer is brought into contact only with an upper surface of the connected wiring layer. As a result, contact resistance cannot be lowered. Furthermore, even if the technique disclosed in JP-A-2002-198421 is applied, the insulating film cannot sufficiently show its function of a spacer depending on the location to which it is retreated, although a contact area can be increased between the connected wiring layer and the upper conductive layer.